A digital cellular radio telecommunication network which incorporates satellite switching centers orbiting the earth faces a dilemma in balancing service quality and service variety against system complexity. Mobile switching centers (MSCs) have been developed to provide a wide range of communication services, including basic and supplementary services, in a terrestrial digital cellular radio telecommunication network and to provide such services at reasonable cost and with reasonable reliability. It would be desirable to incorporate such conventional MSCs into a space-based network to reduce development costs. However, conventional MSCs are relatively complex, ground-based equipment. A space-based network could either sufficiently modify a conventional MSC design to allow the modified MSC to be placed in orbit or route signals propagating in space down to the earth's surface to receive the variety of switching services provided by a conventional MSC.
Placing an MSC in orbit is an undesirable alternative. Placing even a simple satellite in orbit is an expensive undertaking. The large size and weight of a conventional MSC would make an extremely expensive satellite. Moreover, the development effort required to make an MSC withstand a launch and operation in space would further increase costs. In fact, costs could be driven beyond that justified by the demand. Furthermore, complex equipment is more likely to suffer failures than simple equipment. Such complex equipment is better located on the earth where it may be more easily repaired when a failure occurs.
Likewise, placing an MSC on the surface of the earth for use in a space-based network is an undesirable alternative. Signals which travel through a space-based network travel large distances. Propagation delays alone may add many tens of milliseconds delay to communication signals. In addition, various stages of a communication path may add processing delays. Unless care is taken to minimize communication path routing and processing, the combined propagation and processing durations can deteriorate communication service quality by injecting unacceptable delays. Accordingly, the routing of communication signals from a space-based network switching center to the earth to receive the processing and services of an MSC adds a significant and undesirable delay to communication signals, and deteriorates overall service quality.